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Abstract

The mid-infrared wavelength regime 3.5 – 4.1μm, known as the astronomical L’ band is of special interest for exoplanet hunting. Mid-IR compatible photonic technologies are an enabling platform for a range of critical observational science using compact instruments on the next generation of Extremely Large Telescopes. Pupil remapping interferometry is a technique in which subapertures of the telescope pupil (2D) are reformatted into a 1D linear array. This can be done efficiently using 3D photonics. One of the most important techniques to fabricate 3D photonic devices in glass is ultrafast laser inscription. However, common silicate glasses are opaque above 2–2.2 μm and therefore not useful for the fabrication of waveguides at mid-infrared wavelengths. Here we present a study of mid-infrared transparent materials that are compatible with the ultrafast laser inscription technique. This study will inform the development of mid-infrared photonic devices for future exoplanetary discovery.

Tables (4)

Table 1 List of glasses utilised for femtosecond laser fabrication of MIR waveguides. The table also shows the type of glass and their origin. The term IZSBGC represents a family of fluoride glasses with the following fundamental chemical composition: 32InF3-20ZnF2-SrF2-18BaF2-8GaF3-2CaF2.

Table 3 Analysis of the different modification types obtained with a femtosecond laser including the shape of the modification and its sign. See Fig. 2 for a graphic representation of the suitable waveguide (wg) geometry.

Metrics

Table 1

List of glasses utilised for femtosecond laser fabrication of MIR waveguides. The table also shows the type of glass and their origin. The term IZSBGC represents a family of fluoride glasses with the following fundamental chemical composition: 32InF3-20ZnF2-SrF2-18BaF2-8GaF3-2CaF2.

Table 3

Analysis of the different modification types obtained with a femtosecond laser including the shape of the modification and its sign. See Fig. 2 for a graphic representation of the suitable waveguide (wg) geometry.

Table 4

Summary of the results obtained for each glass including the preferred waveguide geometry, the horizontal mode field diameter (MFD) and the refractive index contrast.

Glass name

Preferred Geometry

MFD (1.55 μm)

Δn

As39S61

N1

Multimode

−4 × 10−3

75(GeS2)-15(Ga2S3)-10(CsCl)

P1

8 μm

7 × 10−3

Pr : IZSBGC

P1

20 μm

8 − 9 × 10−4

IZSBGC

P3

Multimode

9 × 10−4

La : IZSBGC

P1

22 μm

8 × 10−4

Ge15Sb20S65

N1

11 μm

−3 × 10−3

Ge11.5As24S64.5

N1

10 μm

−3.5 × 10−3

Ge25As10S65

N3

8 μm

−7 × 10−3

GLS

P2

10 μm

3.5 × 10−3

IRG-2

N2

8.3 μm

−5 × 10−3

Tables (4)

Table 1

List of glasses utilised for femtosecond laser fabrication of MIR waveguides. The table also shows the type of glass and their origin. The term IZSBGC represents a family of fluoride glasses with the following fundamental chemical composition: 32InF3-20ZnF2-SrF2-18BaF2-8GaF3-2CaF2.

Table 3

Analysis of the different modification types obtained with a femtosecond laser including the shape of the modification and its sign. See Fig. 2 for a graphic representation of the suitable waveguide (wg) geometry.